In the formation of high quality pipe welds for both low-alloy and high-alloy steel pipes, for example stainless steel pipes, it is an common practice to bring the pipe ends together at the junction at which the weld seam is to be formed and to supply a welding or protective gas to this site to limit the oxidation and scaling of the weld bead and the adjoining zones of the pipe.
This device can operate from within the pipe and can comprise, according to German patent document DE 33 00 382, for example, a pair of support disks of a heat-resistant elastomer which are disposed on opposite sides of the zone into which the gas is to be released within the pipes assembled for welding. Each of these support disks can be provided at its periphery with a pair of sealing lips which can be ben tin opposite directions from the disk plane. The support disks are mounted at opposite ends of a tube which, between the support disks comprises a body composed of a fine-porous material. A protective gas is fed through this tube and is discharged through this body into the zone flanked by the support disks, and thus enters the junction region of the two pipes in a substantially turbulence-free manner to provide the protective effect without detriment to the welding action.
The device has been found to be successful in use, but its configuration and construction leaves much to be desired when attempts are made to use the device for large-diameter pipes. For example, the stability of the support disks is limited and the device has been found to be less successful for nominal pipe sizes in excess of NW40, utilizing the European pipe standard.